Experimental studies have started in several countries. Using dogs' sense of smell to quickly identify people with Covid-19 could be of great help in the fight against coronavirus. Be careful though. The mechanisms are still unclear, and in any case the nose of dogs has no diagnostic capacity, but should only be understood as a support to screening activities.
HOW DO THEY DO IT?
The canine sense of smell that is already used at airports to snort the presence of explosives, drugs and contraband materials is also successfully used to detect cases of diabetes, malaria and certain types of cancer. During the pandemic, the scientists working in this field therefore came naturally to try to train quadrupeds to recognize CoViD-19 infection, accustoming animals to sniffing sweat and urine of infected patients and receiving a reward for each correct detection. Last July, a team from the University of Veterinary Medicine in Hanover (Germany) found that after a week-long training, dogs distinguish SARS-CoV-2 infected saliva samples with 94% accuracy.
QUESTION OF NOSE.
At the airports of Dubai and Helsinki, a pilot project has been launched with a group of dogs trained to search for potentially infected travelers. How does it work? It's very simple. After landing and collecting their luggage, passengers are asked to wipe the sweat off their necks with a special towel. The sweat samples are placed in some boxes and taken to odorous substances used as a control. At this point the animal goes into action, sniffing the various cans. When he notices the presence of the virus in a sample, he begins to yelp and touch the box with his paw (and in this case the concerned passenger is then subjected to a free swab); if the "test" is negative, it shows no reaction.
The merit goes to their extraordinary sense of smell, with a high concentration of biosensors.
The dog, thanks to a particularly extensive olfactory mucosa (an area of 2 square meters is calculated in the German shepherd against 5 square cm in humans), to the conformation of the nose (presence in the dog of an olfactory recess that guarantees the permanence and analysis of odorants for a longer time), and to the high number of olfactory neurons on the olfactory mucosa itself, it is able to perceive an extraordinarily high quantity of volatile organic substances. Therefore, by taking samples from the patient, the dog is able to report many volatile organic compounds including metabolites derived from viral infections such as Covid 19.
Interesting facts about German Shepherds
Not only extraordinary sense of smell: the canine truffle is able to perceive weak thermal radiations, as if it were an infrared sensor.
A German shepherd has 250 million olfactory cells while the olfactory system of the human being has no more than six million. When he enters a room, the dog explores it through his nose and obtains a real "image". Not a simple snapshot but something more like a video: you see the room, who was there just before and how it moved in space, how it felt, whether it was male or female, conspecific or not.
The olfactory system of the dog (specially in the German shepherd and other breeds) is incredibly developed and not only in the number of cells: on average its olfactory mucosa exceeds 150 square cm (for our species we talk about eight) and its olfactory brain has a number of neurons 40 times higher than that of humans. Its olfactory cortex represents about 12% of the total mass, while the same in humans is a small 1%. The nostrils can move in different directions and thus recognize the origin of a trace. Dogs can distinguish the individual ingredients that make up a smell (while we only perceive the whole), but also identify the source and distance thanks to the ability to interpret information regarding the concentration of substances. It also happens that they get excited when they perceive a smell. And we know that they can discover some human diseases.
See also Top dog breeds sense of smell